That's interesting.  Why would creatinine in the milk be a problem for the
baby.  First of all, do we know it gets into the milk?  And what if it does
at the rate of 10 mg%, say?  The baby would be able to handle that.
Creatinine, incidentally, is not toxic in itself.  It is a marker for renal
function.  The reason seems farfetched to me.  I would encourage this mother
to breastfeed and/or provide her milk.  The risks to the baby, especially a
premature baby, of not getting breastmilk are very high indeed.

Jack Newman, MD, FRCPC